Down syndrome is the most common identifiable cause of intellectual disability and affects all age groups. Prior to the 1970s, most persons with Down syndrome did not survive childhood. Now, 80% reach adolescence, with life expectancy estimates in their mid-50s. Thus, persons with Down syndrome need healthcare from providers who understand both their Down syndrome and their age-/gender-specific medical needs. This becomes difficult in adult-focused medical settings, as the dissemination of medical knowledge surrounding Down syndrome has focused primarily on pediatric settings. As a result, adults with Down syndrome often receive fragmented, suboptimal care that places them at high risk for preventable, irreversible complications of their syndrome. In this study, we seek to establish the relationship between patterns of primary care and their implications for health outcomes in adolescents and adults with Down syndrome. To do so, we will use Medicaid data (the primary payer for persons with Down syndrome) over a 5 year period (2006- 2010) from the states of California, Colorado, Michigan, and Pennsylvania. In Specific Aim 1, we will characterize differences between DS and non-DS adolescents and adults regarding the focus of their primary care physician (child-focused, adult-focused, or mixed focus) and successful adherence to age-/gender- specific guidelines. In Specific Aim 2, we will evaluate differences in adherence to age-/gender-specific guidelines and DS-specific guidelines among adolescents and adults with DS based on the focus of their primary care physician. In Specific Aim 3, we will assess whether differences in successful adherence to age- /gender- and DS-specific guidelines results in changes in healthcare utilization among adolescents and adults with DS. For example, we hypothesize that improved guideline adherence will lead to less frequent high-cost care such as inpatient and emergency encounters. The results of this analysis will serve to identify gaps in the existing care structure of adolescents and adults with DS and to identify characteristics of successful models, all of which are necessary to optimize care delivery and improve health outcomes in this vulnerable population.